Stack Overflow curates its public-facing content, and so do I, when using real-name accounts. Given a choice between being seen taking shit from someone, investing time in arguing with that person, or just erasing the exchange altogether, the third option is sometimes the most expedient. I don't do it often.

Ideally people would just be polite, and questions could just be answered by anyone who cared to answer them, with low-scoring exchanges de-emphasized instead of being shut down.